Leadframe having selective planishing

Abstract

A metal leadframe strip (500) for semiconductor devices is described. The leadframe strip has a plurality of sites (510) for assembling semiconductor chips. The sites alternate with zones (520) for connecting the leadframe to molding compound runners. The sites (510) have mechanically rough and optically matte surfaces (511, 512). The zones (520) have at least portions with mechanically flattened and optically shiny metal surfaces (521, 522). The flattened surface portions transition into the rough surface portions by a step.

Description

FIELD OF THE INVENTION[0001]The present invention is related in general to the field of semiconductor devices and processes, and more specifically to the structure and fabrication process of flood-plated rough metallic leadframes in semiconductor packages having selectively planished portions to reduce the leadframe adhesion to molding compound in zones exposed to compound in mold runners.DESCRIPTION OF RELATED ART[0002]Based on their functions, semiconductor packages include a variety of different materials. Metals formed as leadframes and bonds are employed for mechanical stability and electrical and thermal conductance, and insulators, such as polymeric molding compounds, are used for encapsulations and form factors. In the packaging fabrication flow, it is common practice to attach a plurality of semiconductor chips to a strip of leadframe, to connect the chips to their respective leads, and then to encapsulate the assembled chips in packages, which protect the enclosed parts ag...

AI Technical Summary

Benefits of technology

The patent text discusses the two main trends in the semiconductor market: the need for products that are less sensitive to temperature and moisture levels and the desire to use less expensive process steps. These trends require the development of reliable adhesion between different parts of the semiconductor package and the selection of cost-effective process steps. In response, the patent text identifies leadframe deformation as the root cause of the issue and proposes a solution to prevent it.

Problems solved by technology

In addition, the requirement to use lead-free solders pushes the reflow temperature range into the neighborhood of about 260° C., making it more difficult to maintain mold compound adhesion to the leadframes.

Analyzing quality and productivity issues of molded plastic devices, applicant observed that the process steps of degating after molding frequently causes deformation of the leadframe during the gate removal step.

As a consequence of this deformation, yield losses of approximately 5% may occur at the process step of trimming-and-forming.

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